Alternate method to dependent, nested if statements to check multiple states

Posted by octopusgrabbus on Programmers See other posts from Programmers or by octopusgrabbus
Published on 2012-11-08T18:01:03Z Indexed on 2012/11/08 23:16 UTC
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Is there an easier way to process multiple true/false states than using nested if statements? I think there is, and it would be to create a sequence of states, and then use a function like when to determine if all states were true, and drop out if not. I am asking the question to make sure there is not a preferred Clojure way to do this.

Here is the background of my problem:

I have an application that depends on quite a few input files. The application depends on .csv data reports; column headers for each report (.csv files also), so each sequence in the sequence of sequences can be zipped together with its columns for the purposes of creating a smaller sequence; and column files for output data.

I use the following functions to find out if a file is present:

(defn kind [filename]
  (let [f (File. filename)]
    (cond
      (.isFile f)      "file"
      (.isDirectory f) "directory"
      (.exists f)      "other" 
      :else            "(cannot be found)" )))

(defn look-for 
  [filename expected-type]
    (let [find-status (kind-stat filename expected-type)]
      find-status))

And here are the first few lines of a multiple if which looks ugly and is hard to maintain:

(defn extract-re-values
  "Plain old-fashioned sub-routine to process real-estate values / 3rd Q re bills extract."
  [opts]
  (if (= (utl/look-for (:ifm1 opts) "f") 0)             ; got re columns?
    (if (= (utl/look-for (:ifn1 opts) "f") 0)           ; got re data?
      (if (= (utl/look-for (:ifm3 opts) "f") 0)         ; got re values output columns?
        (if (= (utl/look-for (:ifm4 opts) "f") 0)       ; got re_mixed_use_ratio columns?
          (let [re-in-col-nams  (first (utl/fetch-csv-data (:ifm1 opts)))
                re-in-data      (utl/fetch-csv-data (:ifn1 opts))
                re-val-cols-out (first (utl/fetch-csv-data (:ifm3 opts)))
                mu-val-cols-out (first (utl/fetch-csv-data (:ifm4 opts)))
                chk-results     (utl/chk-seq-len re-in-col-nams (first re-in-data) re-rec-count)]

I am not looking for a discussion of the best way, but what is in Clojure that facilitates solving a problem like this.

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